Osteopontin affects macrophage polarization promoting endocytic but not inflammatory properties
Objective Macrophages are the main drivers of obesity‐induced adipose tissue (AT) inflammation that causes insulin resistance. Macrophages polarize toward different inflammatory (M1) or protective (M2) phenotypes. Osteopontin (OPN) is an inflammatory cytokine highly expressed in AT in obesity and kn...
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Published in | Obesity (Silver Spring, Md.) Vol. 24; no. 7; pp. 1489 - 1498 |
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Main Authors | , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Blackwell Publishing Ltd
01.07.2016
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Subjects | |
Online Access | Get full text |
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Summary: | Objective
Macrophages are the main drivers of obesity‐induced adipose tissue (AT) inflammation that causes insulin resistance. Macrophages polarize toward different inflammatory (M1) or protective (M2) phenotypes. Osteopontin (OPN) is an inflammatory cytokine highly expressed in AT in obesity and known to be involved in chronic inflammatory processes. It was hypothesized that OPN polarizes macrophages into a proinflammatory phenotype.
Methods
AT macrophages (ATMs) of OPN‐deficient (Spp1−/−) and wild‐type C57BL/6 (WT) mice with obesity and bone marrow‐derived macrophages (BMDMs) of Spp1−/− and WT mice as well as human monocyte‐derived macrophages (MDMs) polarized in the presence of OPN were investigated.
Results
While ATM infiltration was lower in Spp1−/− upon high‐fat diet, Spp1−/− ATMs expressed more M1 and less M2 markers but less tumor necrosis factor‐α compared with WT. There was no effect of OPN deficiency on BMDM polarization. In human MDMs, the presence of OPN during polarization ambiguously altered M1/M2‐related marker expression and diminished LPS‐induced inflammatory cytokine production. Strikingly, phagocytic activity was elevated by the presence of OPN during polarization in both human MDMs and murine BMDMs.
Conclusions
In contradiction to our hypothesis, data indicated that OPN does not induce inflammatory macrophages but was a signal to induce phagocytosis, which may be required due to increased adipocyte death in obesity. |
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Bibliography: | Author contribution Supported by the Federal Ministry of Economy, Family and Youth and the National Foundation for Research, Technology and Development (to TMS). The authors declared no conflict of interest. Disclosure KS, MZ, GS and TMS conceived and designed the experiments. Funding agencies KS, BW, KA, ACR, VMV, NG, and LL carried out experiments and analyzed data. All authors were involved in writing the paper and had final approval of the submitted and published versions. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1930-7381 1930-739X |
DOI: | 10.1002/oby.21510 |